This invention relates generally to door locking devices and more particularly to crossbar type door locking devices.
It is well known that conventional door locks may not positively prevent an intruder from breaking into and entering a home. Many of these locks can be quickly unlocked by simply sliding a fairly stiff, thin plastic card between the door and door jamb, so as to slide the bolt out of the jamb and back into the lock. Others using a dead bolt may still be unlocked by a burglar who is skilled in lock picking. Still other unauthorized entry may be made by simply giving the door a sharp kick by a foot, so that the bolt holding fitting mounted in the door jamb will split the wood of the jamb and will be pushed out from the jamb. Even the use of long mounting screws for this fitting cannot prevent such break-in if the door jamb wood is weakend by becoming rotted or dried out so as to easily split.
A number of device have been devised to overcome this problem. For example, U.S. Pat. No. 3,792,885 describes a double bar lock having oppositely extending locking bars that are mechanically extended or retracted by means of a mechanical latch. U.S. Pat. No. 4,176,347 describes a dead bolt device having an alarm attached thereto. U.S. Pat. No. 4,349,223 describes a sliding bolt for sliding across the inner side of a door of a home in which a two directional electric motor moves the bolt through U-shaped brackets mounted on the rear of the door and also on the wall adjacent each side of the door. U.S. Pat. No. 2,070,803 describes a safe having a door locking mechanism including an electric motor for moving two locking bars into engagement with the walls of the safe so as to lock it until such time as the electric motor is actuated.
The above listed devices, however, do not solve the problem of having a light, inexpensive, easily removable door locking mechanism which may be selectively attached to the door and operated manually, by an electric timer; or from a remote location.